We describe a male patient with lung adenocarcinoma who possessed the germline EGFR T790M mutation along with somatic mutations in EGFR 19-Del, TP53, and PIK3CA. This specific combination of mutations is extremely rare, with the first reported case of a patient having both germline EGFR T790M and somatic EGFR L858R and PIK3CA mutations documented by Lammers et al. [21]. Here, TP53 is linked to lung adenocarcinoma.